THE CODLING MOTH IN MICHIGAN. 



45 



The eggs for these experiments were kept in the outdoor rearing 

 shelter, subjected to the normal temperature. 



It should be remembered that throughout these tests the tem- 

 perature has been fluctuating and that the separate obsevations can 

 be only approximately exact and we have therefore obtained a great 

 latitude of variation in degrees of temperature for the respective days. 

 The extent of this variation is shown in Tables XLYI and LX in the 

 maximum and minimum records. Variation in the time of incuba- 

 tion should not entirely be ascribed to inadequate methods of record- 



• *first brood; o'SeconcJ Broocf of eqqs 



Fig. 15. — Curve shoeing relation of the temperature to the time of incubation of first-brood and second- 

 brood eggs of the codling moth at Douglas, Mich. , 1911. (From Tables XLEI and LVII.) (Original.) 



ing observations but also to natural influences other than tempera- 

 ture. It has been constantly found that eggs deposited at the same 

 time have varied several days in hatching. Moisture conditions no 

 doubt also have a bearing upon the length of incubation. The 

 writer has found that eggs do not hatch readily during the prevalence 

 of extremely dry weather. 



The "critical" temperature for the eggs of the codling moth can 

 not be determined from the present data. It is therefore not possible 

 to establish the degrees of accumulated effective temperature required 

 for hatching under any given degrees of temperature. 



